Employees at the Synthron Inc. plant were making a paint additive in the 1,500-gallon reactor when chemical vapor escaped just before the explosion, said Jim Lay, lead investigator with the U.S. Chemical Safety and Hazard Investigation Board. The process uses the chemical butyl acrylate along with flammable solvents and generates significant amounts of heat.

According to Lay, workers at Synthron Inc. only made the paint additive about once or twice a year.

"An important focus of our investigation will be to understand what was different about conditions on Jan. 31 that could have caused the major accident that occurred," Lay said.

State labor officials say their investigation into the explosion has been delayed because the structure is near collapse and no one has been able to enter.

"No one has been able to step inside to begin a physical examination of the evidence," Labor Commissioner Cherie Berry said this week. "We're anxious to find the cause of the accident, but we don't want to risk the lives of others while that building is teetering like that."

Some workers at Synthron reported hearing a loud hiss minutes before the explosion and escaped, but even some who were outside were thrown as far as 20 feet, the chemical board has said.

All 12 employees on duty at the time and some passersby were injured in the blast, which leveled much of the plant and blew out windows up to a third of a mile away.

<p class="bold allcaps">UPDATED: 12:45 p.m. <br></p>
<p>A leak from a chemical reactor was the most likely cause of the January plant explosion that killed one man and injured at least a dozen others, federal safety investigators said Wednesday.</p><p>Employees at the Synthron Inc. plant were making a paint additive in the 1,500-gallon reactor when chemical vapor escaped just before the explosion, said Jim Lay, lead investigator with the U.S. Chemical Safety and Hazard Investigation Board. The process uses the chemical butyl acrylate along with flammable solvents and generates significant amounts of heat.</p><p>According to Lay, workers at Synthron Inc. only made the paint additive about once or twice a year.</p><p>"An important focus of our investigation will be to understand what was different about conditions on Jan. 31 that could have caused the major accident that occurred," Lay said.</p><p>The explosion virtually destroyed the plant. Curtis "Butch" Brackett, the plant's facilities maintenance head, died after suffering severe burns.</p><p>State labor officials say their investigation into the explosion has been delayed because the structure is near collapse and no one has been able to enter.</p><p>"No one has been able to step inside to begin a physical examination of the evidence," Labor Commissioner Cherie Berry said this week. "We're anxious to find the cause of the accident, but we don't want to risk the lives of others while that building is teetering like that."</p><p>Some workers at Synthron reported hearing a loud hiss minutes before the explosion and escaped, but even some who were outside were thrown as far as 20 feet, the chemical board has said.</p><p>All 12 employees on duty at the time and some passersby were injured in the blast, which leveled much of the plant and blew out windows up to a third of a mile away.</p>